Pressure sensitive device for operating a switch or the like

ABSTRACT

A pressure sensitive device for operating an electrical switch or the like comprises a body having walls defining a chamber within which is a flexible diaphragm. A pressure fluid conduit communicates with the chamber on one side of the diaphragm and a reciprocable piston extends into the chamber on the other side of the diaphragm so as to be displaceable in one direction by the diaphragm in response to the introduction of pressure fluid to the chamber via the conduit. The piston is encircled by a resilient, annular cushioning member which engages both the piston and the diaphragm to form a cushioned bridge between the piston and the diaphragm. Movement of the piston a predetermined distance in one direction effects actuation of an instrumentality such as an electrical switch, and the piston is biased by a spring to move in the opposite direction.

United States Patent Hawke PRESSURE SENSITIVE DEVICE FOR OPERATING A SWITCH OR THE LIKE Inventor:

Assignee:

Filed:

Earle G. Hawke, Clarkston, Mich.

The Nason Company, Clarkston,

Mich.

Aug. 28, 1972 US. Cl 92/101, 92/5 R, 92/94,

Int. Cl. F01b 19/00, Fl6j 3/00 Field of Search 92/95, 101, 102, 98 RD,

92/5 R; 200/83 B, 83 J References Cited UNITED STATES PATENTS Riley ZOO/83 J Primary Examiner--lrwin C. Cohen Assistant Examiner-Abraham Hershkovitz Attorney, Agent, or Firm-Learman & McCulloch 5 7] ABSTRACT A pressure sensitive device for operating an electrical switch or the like comprises a body having walls defining a chamber within which is a flexible diaphragm. A pressure fluid conduit communicates with the chamber on one side of the diaphragm and a reciprocable piston extends into the chamber on the other side of the diaphragm so as to be displaceable in one direction by the diaphragm in response to the introduction of pressure fluid to the chamber via the conduit. The piston is encircled by a resilient, annular cushioning member which engages both the piston and the diaphragm to form a cushioned bridge between the piston and the diaphragm. Movement of the piston a predetermined distance in one direction effects actuation of an instrumentality such as an electrical switch, and the piston is biased by a spring to move in the opposite direction.

6 Claims, 3 Drawing Figures PRESSURE SENSITIVE DEVICE FOR OPERATING A SWITCH OR THE LIKE Pressure sensitive, diaphragm actuated devices for operating electrical switches and the like are well known. Devices of this kind conventionally comprise a housing having a chamber therein and in which is mounted a displaceable diaphragm which acts upon a reciprocable piston or plunger so as to shift the latter in response to changes in pressure within the chamber. One of the difficulties frequently encountered with such pressure sensitive devices, and particularly those intended for use in systems operating at pressures in excess of 1,000 p.s.i., is that the diaphragms become worn, torn, stretched, or otherwise misshapen in the areas of engagement between the diaphragm and the piston with consequent failure of the diaphragms and shortening of the useful life of the device.

Failures of diaphragms due to the reaction between them and the piston are directly proportional to the pressures encountered. In an effort to minimize diaphragm failure and thereby prolong the life of the devices associated therewith, two diaphragms in face-toface engagement have been used. In such a construction, the inner diaphragm, that is, the one which engages the piston, is subjected to the greater wear, at least initially, thereby prolonging the life of the device. Once the inner diaphragm becomes worn, however, the other diaphragm is subjected to wear and at an accelerated rate. Although the use of dual diaphragms does aid in prolonging the life of the device in which they are incorporated, the dual diaphragms are less sensitive than a single diaphragm and wear of either or both of the diaphragms has an adverse effect on the operating characteristics of the device.

An object of this invention is to provide a pressure sensitive actuating device incorporating a displaceable piston and a flexible diaphragm and wherein a resilient cushioning element bridges the relatively movable parts of the piston and diaphragm so as to avoid wear and failure of the diaphragm.

Another object of the invention is to provide a pressure sensitive device of the character referred to and wherein the manufacture and assembly of the parts are extremely simple and inexpensive.

A further object of the invention is to provide a pressure sensitive device of the kind described and which is capable of functioning satisfactorily over extremely wide, high pressure ranges.

Other objects and advantages of the invention will be pointed out specifically or will become apparent from the following description when it is considered in conjunction with the appended claims and the accompanying drawings, in which:

FIG. 1 is an elevational view of a pressure sensitive device constructed in accordance with the invention, certain parts being broken away for illustrative purposes;

FIG. 2 is a vertical sectional view of the apparatus shown in FIG. 1, but with the housing removed and the remaining structure rotated counterclockwise through 90; and

FIG. 3 is a sectional view taken along the line 3--3 of FIG. 2.

Apparatus constructed in accordance with the invention comprises a two-part body 1 comprising a disc-like base 2 and a cover 3, both of which preferably are formed of metal. The inner surface 4 of the base 2 is flat and the confronting surface 5 of the cover 3 also is flat except for a centrally located recess 6 which forms a chamber 7 within the body. Interposed between the confronting surfaces of the base and the body is a flexible, fluid impervious diaphragm 8. The body parts 2 and 3 and the diaphragm 8 are provided with openings for the accommodation of a p'lurality of circumferentially spaced bolts 9 by means of which the parts are maintained assembled in fluid-tight relation.

Carried by the base 2 is a pair of spaced apart, upstanding brackets 10 and 11 joined at their upper ends by a cross member 12 provided at its opposite ends with upstanding legs 13. The cross member 12 is upset between its ends to form an interiorly threaded socket 14 in which is fitted an exteriorly threaded, hollow adjusting screw 15.

A piston 16 is carried by the base 2 and comprises a smooth, elongate stem 17 terminating at one end in an enlarged head 18 that is reciprocable in a bore 19 formed in the base. The bore 19 communicates with a reduced diameter bore 20 which, together with the bore 19, forms a shoulder 21 which limits movement of the piston 16 upwardly as viewed in FIG. -2. The free end of the piston head 18 bears directly against the diaphragm 8, and the peripheral edge of the piston head preferably is chamfered as at 22.

Slidably mounted on the piston stem 17 is a ferrule 23 of such diameter at one end as to fit within the bore 20, and having a peripheral flange 24 between its ends. The flange seats on the base 2 to limit inward movement of the ferrule and the adjacent end of the ferrule seats on the head 18. The other end of the ferrule is of lesser diameter so as to fit within a coiled compression spring 25 which encircles the stem 17. The spring 25 bears at one end against the screw 15 and at the other end against an arm 26 that is slidably mounted on the ferrule 23 and includes an extension 27. The extension 27 engages an instrumentality to be operated, such as a reciprocable plunger 28 forming part of a conventional snap-action electrical switch having a casing 29 that is bolted or otherwise suitably fixed to the bracket 10. Terminals 30 and 31 project through the casing 29 and are connected to the switch contacts (not shown) within the casing.

The cover 3 of the body has an exteriorly threaded nipple 32 having an axial bore 33 communicating with the chamber 7 and forming a conduit by means of which pressure fluid may flow to and from the chamber. The nipple 32 may be threaded as at 34 so as to permit it to be screwed into a fitting formed in a hydraulic or pneumatic pressure line (not shown).

Those parts of the apparatus mounted on the base 2 preferably are enclosed within a cup-shaped housing 35 having a skirt 36 which snugly accommodates the peripheral edge of the cover 3. The housing 35 preferably carries conductive terminals 37 and 38 which may be joined by wiring (not shown) to the switch terminals 30 and 31, respectively.

The apparatus thus far described is substantially conventional in pressure responsive, diaphragm actuated switch operating mechanisms, and form no part of the invention except insofar as it cooperates with the structure subsequently to be described.

As has been referred to earlier, the piston head 18 is accommodated in a bore 19 formed in the base 2. The bore 19 communicates with a right angular counterbore 39 which extends inwardly from the surface 4 of the base 2. At the juncture of the bore 19 and the counterbore 39 is a shoulder 40. Accommodated in the counterbore 39 is a resilient, annular cushioning member 41, such as a rubber, neoprene, or other rubbery O-ring which encircles the piston head 18 and seats on the shoulder 40. The outside diameter of the ring 41 corresponds to the diameter of the counterbore 39, and the inside diameter of the ring 41 corresponds to the diameter of the head 18, and the length of the head 18 corresponds substantially to the distance from the surface 4 to the shoulder 21. The diameter of the ring 41 corresponds substantially to the depth of the counterbore 39, and preferably is 0.0l-0.030 inch greater than the depth of the counterbore so as normally to protrude slightly beyond the surface 4. The ring 41, therefore, constitutes a resilient bridge between the periphery of the counterbore 39 and the flat surface of the piston head 18.

To condition the apparatus for operation, the nipple 32 is threaded into a fitting carried by a pressure fluid line so that fluid from the line may enter the chamber 7 via the bore 33. The screw may be adjusted so as to vary the force exerted by the spring 25 on the ferrule 23, the arm 26, and the piston 16, thereby precluding movement of the piston 16 upwardly from the position shown in FIG. 2 until such time as the force exerted on the piston via the diaphragm 8 exceeds the force exerted on the piston by the spring 25.

When the forcelexerte'd on the piston via the diaphragm 8 exceeds the force exerted on the piston by the spring 25, the piston will be displaced axially to the extent permitted by the shoulder 21 and the diaphragm 8 will be deflected in such direction as to follow the movement of the piston. Such movement of the piston is limited by the shoulder 21 to an extent less than the depth of the counterbore 39, but will effect corresponding movement of the leg 27 of the arm 26 so as to depress the switch operator 28 to close the switch contacts and energize a signal. When the force of the fluid pressure in the chamber 7 is relieved, the spring 25 will restore the piston and its associated parts to the positions shown in FIG. 2.

During movements of the piston 16 that portion of the diaphragm 8 which engages the surface of the piston head 18 will remain in engagement therewith and that portion of the diaphragm in engagement with the surface 4 of the base 2 will remain in engagement therewith. The only portion of the diaphragm which is deflected, therefore, is that portion which overlies the ring 41. Flexure of the diaphragm during movement of the piston head into the bore 19 is yieldably resisted or cushioned by the ring 41 which is capable of being deformed into the counterbore 39 in view of the right angular configuration of the latter. Thus, during inward movement of the piston head, the deformation of the ring 41 provides a yieldable support for the flexing portion of the diaphragm and prevents relative sliding movement of the diaphragm and the piston and also prevents stretching of the diaphragm around the head of the piston. As a consequence, frictional wear and stretching or extruding of the diaphragm are prevented.

The effectiveness of the disclosed construction has been tested by subjecting devices corresponding to the disclosed embodiment to many thousands of cycles of operation at a pressure of 3,000 psi. with no discernible evidence of diaphragm wear. The life of a device constructed in accordance with the invention greatly exceeds that of conventional devices.

Although the disclosed embodiment illustrates the use of a single diaphragm only, two or more diaphragms in face-to-face engagement may be used, if desired.

The disclosed embodiment is representative of a presently preferred form of the invention, but is intended to be illustrative rather than definitive thereof. The invention is defined in the claims.

What is claimed is:

l. A pressure sensitive device comprising a body having walls defining a chamber; a flexible diaphragm spanning said chamber; pressure fluid conduit means in communication with said chamber on one side of said diaphragm; a bore in communication with said chamber on the opposite side of said diaphragm; a reciprocable piston extending through said bore and terminating at and abutting said opposite side of said diaphragm, said piston being movable in response to the introduction and exhaust of pressure fluid to and from said chamber via said conduit means; a counterbore surrounding said bore and being of less depth than that of said bore; an annular cushioning member constantly occupying said counterbore and encircling said piston, said cushioning member spanning the distance between said piston and the periphery of said counterbore and having a thickness greater than the depth of said counterbore whereby said cushioning member engages said diaphragm and forms a resilient bridge for the latter between said piston and the periphery of said counterbore; and means for. limiting movement of said piston in a direction outwardly of said chamber a'distance greater than the depth of said'counterbore.

2. A device according to claim 1 including an instrumentality to be operated in response to movement of said piston in said outwardly direction, and actuating means operable in response to predetermined movement of said piston in said outwardly direction to operate said instrumentality.

3. A device according to claim 1 including spring means acting on said piston and urging the latter to move in an opposite direction to said outwardly direction.

4. A device according to claim 1 wherein said cushioning member comprises a deformable, rubbery ring.

5. A device according to claim 1 wherein said cushioning member is circular in cross-section and wherein said counterbore is right angular in cross-section.

6. A device according to claim 1 including means in the path of movement of said piston to limit movement of said piston in an opposite direction to said outwardly direction. 

1. A pressure sensitive device comprising a body having walls defining a chamber; a flexible diaphragm spanning said chamber; pressure fluid conduit means in communication with said chamber on one side of said diaphragm; a bore in communication with said chamber on the opposite side of said diaphragm; a reciprocable piston extending through said bore and terminating at and abutting said opposite side of said diaphragm, said piston being movable in response to the introduction and exhaust of pressure fluid to and from said chamber via said conduit means; a counterbore surrounding said bore and being of less depth than that of said bore; an annular cushioning member constantly occupying said counterbore and encircling said piston, said cushioning member spanning the distance between said piston and the periphery of said counterbore and having a thickness greater than the depth of said counterbore whereby said cushioning member engages said diaphragm and forms a resilient bridge for the latter between said piston and the periphery of said counterbore; and means for limiting movement of said piston in a direction outwardly of said chamber a distance greater than the depth of said counterbore.
 2. A device according to claim 1 including an instrumentality to be operated in response to movement of said piston in said outwardly direction, and actuating means operable in response to predetermined movement of said piston in said outwardly direction to operate said instrumentality.
 3. A device according to claim 1 including spring means acting on said piston and urging the latter to move in an opposite direction to said outwardly direction.
 4. A device according to claim 1 wherein said cushioning member comprises a deformable, rubbery ring.
 5. A device according to claim 1 wherein said cushioning member is circular in cross-section and wherein said counterbore is right angular in cross-section.
 6. A device according to claim 1 including means in the path of movement of said piston to limit movement of said piston in an opposite direction to said outwardly direction. 